docs: async def add_message(self, request):
          """Registers a new message for the user."""
          session = await get_session(request)
          user_id = session.get('user_id')
          if not user_id:
              raise web.HTTPNotAuthorized()
          form = await request.post()
  
          if form.get('text'):
              user = await self.mongo.user.find_one(
                  {'_id': ObjectId(session['user_id'])},
                  {'email': 1, 'username': 1})
  
              await self.mongo.message.insert(
                  {'author_id': ObjectId(user_id),
                   'email': user['email'],
                   'username': user['username'],
                   'text': form['text'],
                   'pub_date': datetime.datetime.utcnow()})
          return redirect(request, 'timeline')